Here is the full list of all 42 Knights of Pen and Paper +1 achievements. It takes around 20-25 hours to unlock all of the achievements on Windows.
Kill a dragon.
Unlock all masters.
Visit every single place in game.
Unlock the Necromancer class.
Unlock the Shaman class.
Spend 9.001 golds.
Earn 9.001 golds.
Reach Level 30 in any character.
Reach Level 30 in a trio.
Reach Level 30 in every character of your group.
Reach Level 15 in a specific Spell.
Unlock the Knight class.
Unlock a new master.
Gather 10 grindstones from veins.
Clear a dungeon.
Unlock the Hunter class.
Gather a grindstone by mining veins.
Unlock the Barbarian class.
Use a potion while full health.
Unlock the Bard class.
Reach Level 15 in any character.
Win a battle with 7 monsters.
Unlock the Game Developers that made the game.
Make the blacksmith dance.
Roll 1 in any random roll.
Reach Level 5 in any character.
Roll 20 in any random roll.
Kill an elite minion.
We know it may be frustrating to die so we've just rewarded you with this achievement. Do not give up, the game is about to begin!
Continue the game after a game over.
Complete a campaign using all 5 Game Developers as characters.
Play with all classes in game.
Play with all characters in game.
Visit your Kitchen inside the game.
Buy the highest weapon upgrade available.
Buy the highest armor upgrade available.
Finished the campaign.
Choose a weird combination of character and class.
Finish the storyline as fast as you can (less than 365 days but you may extend that to 465).
Buy all goodies in game.
Clear 10 dungeons.
Clear 50 dungeons.